Typically, nappies comprise an impermeable layer, for example of polyethylene, a layer of non-woven fabric permeable to liquids and an absorbent pad sandwiched therebetween.
Nappies also comprise a liquid acquisition layer interposed between the absorbent pad and the permeable layer of non-woven fabric in order to promote liquid distribution in the absorbent pad.
Absorbent pads are made mainly from natural fibre particles (known as “fluff”) uniformly blended with particles of superabsorbent polymer material (“SAP”).
In recent years, higher pad absorption capacity has been achieved by absorbent pads comprising one or more discrete absorbent layers made mainly from particles of superabsorbent polymer material (“SAP”).
Known from the prior art is a unit for making absorbent pads for nappies and comprising a drum, which rotates about its axis of rotation and which has on its peripheral cylindrical surface a plurality of suction housings or recesses within which respective absorbent pads are formed.
The unit also comprises a hood for feeding the particles of fluff mixed with the particles of “SAP” and which is mounted along a stretch of predetermined width above the peripheral cylindrical surface and the corresponding suction recesses.
Once a suction recess on the drum has been filled with fluff mixed with the “SAP”, fed by the hood, a respective finished absorbent pad is obtained.
During the formation of the absorbent pads in the suction recesses, the feeding duct intermittently feeds the “SAP” directly into the suction recesses on the drum, thus defining the above mentioned discrete absorbent layers.
It has been found, however, that the “SAP” fed into the suction recesses does not settle on top of the mixture of fluff and “SAP” already present in each suction recess but penetrates into it, thus spoiling the absorbent pad being formed and negatively affecting the quality of the finished absorbent pads.